1. Field of the Invention
This invention is an anchoring device especially designed to be used with an extensometer.
2. Description of the Prior Art
The concept of using retaining rings that are placed in grooves of a member to be retained so that the rings expand outwardly to anchor the member is known. The United States patent to W. G. Tilton (U.S. Pat. No. 502,686) shows this arrangement wherein there are grooves in one member and also grooves in a shaft coupling that is retained thereon. Normally the retaining rings are compressed (page 1, line 42) or loaded--presumably by hand, pliers, etc.-- and then held by the outer coupling until the sets of grooves of the coupling and member are aligned to coincide as one is moved relative to the other. Then the compressed loaded rings spring outwardly to anchor the members together.
Another reference (U.S. Pat. No. 929,979 to H. W. Pleister) discloses expanders 17 mounted in a slot 12 and a split ring 22 used to hold the expanders together in handling and shipping. Still other reference (U.S. Pat. No. 2,388,841 to D. W. Goodwin) discloses a spring shoe 60 with a set screw 71 to vary the friction (page 2, lines 62-73). A split ring with holes 23 used to receive tools to move the ring is disclosed in U.S. Pat. No. 2,491,306 to R. Feitl. Two U.S. patents--U.S. Pat. Nos. 3,535,750 and 3,698,278 to J. R. Metz and W. H. Trembley, respectively--disclose the idea of an outwardly biased locking member which is actuated by a pull device.
Perhaps the closest prior art to applicant's invention is the U.S. Pat. No. 2,712,952 to K. I. Lundgren. Therein a resilient ring 1 has holes at lugs 2 to receive the bolts 3. As the nuts 5 on the bolts are tightened the ring becomes fixed in the grooves 8. The FIG. 6-8 embodiment uses recesses 18 in the ring to lock it in cooperation with the bolt 19 (column 2, lines 21 et seq.)
Although the prior art discloses many of the essential features of the present invention, it fails to suggest or disclose the totality thereof or most of them used for the same or a similar purpose. None discloses an anchor body which is locked in a borehole by a preloaded resilient member placed in a groove of the anchor body which member has provision to hold the member in a loaded position by a pullable retaining member extending outside the borehole and unload the member by actuating the retaining member. None discloses a similar system useable with a extensometer anchor that is placed in a mine borehole and simply actuated by pulling a member located outside of the borehole.